Preheat the grill to medium heat and prepare a large sheet of heavy-duty aluminum foil. You’ll make a quiet bed for the potatoes so they cook evenly and stay moist.

Wash the sweet potatoes well and pat dry. Slice them into even rounds about 1/2 inch thick, or cut into thick wedges depending on your preference. Keeping the pieces roughly the same size ensures uniform cooking.

In a bowl, whisk together olive oil, honey, mustard, apple cider vinegar, minced garlic, salt, pepper, and lemon juice if using. The mixture should be glossy and slightly thick so it sticks to the potato pieces.

Toss the potato slices in the glaze until well coated. Lay a sheet of foil on the counter, then spread a light layer of the glaze on the foil. This creates a thin, nonstick surface and adds flavor from the bottom up.

Arrange the coated potatoes on the foil, overlapping slightly but not crowded. Fold up the sides of the foil to create a loose pan; this acts like a mini steamer and keeps the potatoes juicy.

Seal the foil packet tightly but leave a small air pocket for steam. Place the packet on the grill and cook for about 15–20 minutes, turning once halfway through, until the potatoes are tender when pierced with a fork.

Carefully open the foil to release steam. If you like a caramelized finish, move the packet directly over the grill grates for 1–2 minutes per side, watching closely to prevent burning.

Remove from heat, let rest for 3–5 minutes, then drizzle with any remaining glaze from the bottom of the foil. Garnish with chopped herbs if you like, and serve warm.